Method of treating lubricating oil stocks



Sept. 26, 1933. 1.. DAVIS ET AL 1,927,823

METHOD OF TREATING LUBRICATING OIL STOCKS Filed NOV. 23, 1928 PRESS C 0N TACT' PLANT FILTER sETTL/NG ANKS HWY AG/ TATOR OXIDATION AIR TO SPIDER A/R TO S P/DER INIENTOI? Zloya'LDavis and Graeme LA ikinson BY My Patented Sept. 26, 1933 UNITED STATES PATENT OFFICE IHETHOD OF TREATING LUBRIUA'I'ING OTL STOCKS ware Application November 23, 1928 Serial No. 321,333

4 Claims.

This invention relates to improvements in the treating of lubricating distillates or oils in such a manner as to produce light colored oils, especially the highly viscous light colored lubricants, in a more emcient manner and also to efiect a lowering of the carbon residue.

Among the salient objects of the present invention are: to produce a comparatively highly viscous lubricating oil of a comparatively light color; to increase the quantity of production of such a product at less cost of producing than by the ordinary method of refining; to successfully produce a highly viscous light colored oil through one cycle of operation; to decrease the amount of filtering that is usually required in producing the light colored oils in the usual way of refining; to produce a light colored product which is lower in carbon residue than that obtained by the usual method of refining; to permit the use of stronger acid, with an improvement of the quality of the resulting by-product sludge.

The common and accepted methods of processes in treating lubricating distillates or oils for the production of light colored lubricating oils have essentially the following steps:

In the acid alkali method, the distillate or oil 'is agitated with sulphuric acid, followed by setfullers earth until the desired color is obtained.

Another well lmown method is to treat the lubricating distillate or oil with sulphuric acid, settling out sludge, contacting the oil with fine fullers earth, removing the fine fuller's earth by filter presses or other means and filtering through fullers earth to the desired color. In the production of light colored viscous oil of paraffin base source, the oil after contacting with and removal of fine fullers earth is blended with naphtha, chilled and wax removed, distilled to remove naphtha and filtered through fullers earth to the desired color.

The demand for large quantities of light color, highly viscous lubricating oils, generally known as Bright Stocks and other highly viscous lubricating oils, have made it desirable to find a process to produce light colored oils, to increase the quantity of production at less cost than by the ordinary method of refining and to produce a product having a lower carbon residue than by the usual method of refining.

The present invention or method consists of the complete dehydration of the oil and the controlled oxidation of highly unsaturated hydrocarbons to a predetermined point. It has been found that the oxidation by air or oxygen must be controlled in order to produce the optimum result.

It is recognized that present common methods of preparing lubricating stocks for acid treating contemplate a certain degree of dehydration. The present method, however, requires that the oil stock to be treated is made entirely or completely moisture free. Oil stocks when dehydrated according to our requirement in our method has no detectable water content.

In, carrying out this process it has been found 10 that in certain cases it is advisable to first dehydrate the oil and then to oxidize it to a desired point, while with certain oils it is possible to carry out the dehydration and oxidation by air or oxygen simultaneously. The dehydration step, as suggested, is sufliciently exhausive of the moisture content to eliminate any trace of detectable water or moisture. This type of dehydration is considerably more stringent than the usual dehydration methods. The chief purpose in the refining of lubricating oil with chemicals such as sulphuric acid is to remove the unstable color forming materials, which in general can be classified as asphalts, asphalt forming materials, asphaltgens, gummy or resinous material, or highly unsaturated hydrocarbons. The hydrocarbons are acted upon by air or oxygen to form complex oxygen carrying and/or polymerized hydrocarbon materials.

These oxidized and/or polymerized compounds are much more readily and completely acted upon by sulphuric acid than are the original compounds. The action of sulphuric acid in the removal of these compounds may be either direct combination of the sulphuric acid with the hydrocarbon to form materials insoluble in the oil and/or direct solution of the coloring materials in sulphuric acid and/or coagulation of the colloid-like particles causing them to precipitate. I In addition to the effect of the oxidation and 1 polymerization of the unsaturated hydrocarbons, it has been found that the minutest traces of water present in the oil seriously affect the action of the acid upon the oil and the best results are obtained only when the oil is completely dehydrated.

' The process resulting in the oxidation and/or polymerization of the highly unsaturated hydrocarbons before the usual chemical treatment seems to change the nature of the unstable color forming material, so that in acid treating a more complete removal of such compounds is effected than would be possible by the usual method.

Another effect of this process is the more com-- customary method. When refining an oil with sulphuric acid, said oil not having been previously dehydrated and oxidized, the resulting sludge is more coke-like and difiicult to 'remove from the agitator or reaction vessel, has a tendency to remain in suspension in the oil (in the form of pepper sludge) and the recovery of the acid from the sludge is more diflicult than when the oil has been previously dehydrated and oxidized. The sludge secured from an oil which has been dehydrated and oxidized previous to the refining with sulphuric acid is of ribbon-like character, is easily drawn from the agitator or reaction vessel, and

very little pe per sludge remains in the oil. Also the sludge is very easily handled in the separating kettles, which are a part of the acid recovery plant. The separation of a sludge of ribbon-like instead of coke-like character is of great value in the practical operation of oil refining. In the art of acid treating lubricating oil stocks, two distinct general types of acid sludge are obtained. One type is known .asribbon like sludge; the other is referred to, depending on its character as hard sludge", grainy sludge,

and fibrous sludge; etc. In an acid treat which yields a ribbon like sludge, the separation and settling of acid sludge from the oil are usually quickly and practically completely accomplished.

In other words, less .pepper sludge remains in the treated stock. The settled sludge is easily drawn off without loss of occluded oil in the form of a homogeneous mass of sludge resembling in some respects a ribbon, from which its name is derived. In other types of sludge the contrary is true, that is, slower separation and slower settling and more sludge pepper remaining in the oil stock; The settled sludge, therefore, is not a homogeneous mass but has considerable oil stock occluded therein. In the latter case the sludge is not cohesive but remains in suspension in the treated oil in the form of hard conglomerates.

When this type of sludge is drawn, the stream of sludge and oil will not form a long ribbon but will have a tendency to break between the batches of sludge conglomerates removed. should be emphasized that in the refining of dis tillates or highly viscous oils which go to make up the lubricants, it is often desirable to use a verystrong acid, if practicable operating conditions will permit, and this process eliminates these difilculties encountered in the processing of various distillates and highly viscous oils.

This invention is applicable to any distillate or oil used in the manufacture of lubricating oil and the' strength of acid may be varied, as various s of oils may require different strengths of acid. Ninety-eight percent sulphuric acid has been found preferable in the treating of certain types of oils. The temperature of oxidation is to some extent interchangeable with time and it is preferred to oxidize at 200 F. to 300 F.

It is not the intention to limit the temperature of oxidation to these points. 1

The following is a description of one preferred method of operation of this process and is oifered in the interest, of'clarifying the disclosure and it is not to be considered as a limitation thereto, as it is appreciated that the method is capable of innumerable modifications.

The single figure shown in the drawing is a schematic diagram of the equipment and method of carrying out the process.

From the storage tank 1 the oil is pumped through exchanger 2 to the dehydrator 3 where the water is removed, and the oil next passes through exchanger 4 where the oil is brought to the desired temperature for oxidation. From exchanger 4 the oil next passes into a tank 5 in which the oxidation of the oil is carried out by bubblingair or oxygen through the oil until theoxidation reaches a predetermined point. With some oils it is possible to pump from storage tank 1 directly through heat exchanger 4 or any suitable means of obtaining the desired temperature for the oxidation tank 5. After the oil has been oxidized to a predetermined point, the oil then passes through exchanger dwhere the oil is cooled to-the temperature in the neighborhood of 135 F.

or thereabout at which the oil is to be preferably treated with sulphuric acid. The oil is treated with sulphuric acid in agitator 7, and the bulk of the resulting sludge withdrawn. The treated oil is then transferred to settling tank 8 in which it is kept for a sufilcient length of time to permit the balance of the sludge in the form of fine particles known as pepper sludge to settle out. After settling out the pepper sludge in tank 8, the oil is then finished to desired specifications by any one of several well known methods. The

finishing steps include decolorization, wax removal when necessary, and other stages of purification.

We have found that the above method of treating and refining results in the improvement stated, namely that of getting a greatly improved lighter color and of making a product with much lesser carbon-forming tendency than possible in the ordinary well-known way.

The following is an example of the dehydration-oxidation process on a typical Mid-Continent cylinder stock. The cylinder stock was dehydrated and oxidized with air at a temperature of 290 F. to 300 F. The oil was blown for 50 minutes and then cooled and acid treated in an agitator at' 135 F. with 40 pounds per barrel of 98% sulphuric acid in two dumps of 20 pounds each, drawing the sludge after each dump of acid. The oil. after treating, was contacted with fine fuller's earth, with a resulting color of 5 on a Tag-Robinson colorimeter. The oil and clay vmixturewas then blended with naphtha and the clay filtered out. Then the solution was chilled to a temperature of minus 15 F. and the wax removed by centrifuging and the naphtha removed by distillation, with a resulting pour test of 20-25. If lower temperature were used the resulting pour test would be lower.

The ordinary method of treating the same oil with 40 pounds per barrel of 98% sulphuric acid in two dumps of 20 pounds each and drawing sludge after eachdump of acid and contacting with an equal quantity of fullers earth as that used in the dehydration and the oxidation process gave a resulting color of 2 on a Tag: Robinson colorimeter, thus showing a distinct improvement in color by our dehydration-oxidation process.

The ordinary method of treating the same oil with 40 pounds of 98% sulphuric acid, drawing sludge and contacting with the same quantities of fullers earth and without dehydration and oxidation gave a resulting carbon residue of 1.76% as compared to 1.25% carbon residue ob-- tained by our dehydration-oxidation process.

As previously stated, the sludge from the treatment without dehydration and oxidation was coke-like in character while the sludge from our dehydration and oxidation method was ribbonlike, more easily handled and gave better results in recovering the acid.

It will be understood that the foregoing description does not necessarily represent and is not intended to represent, the exact treatment for all oils, as the quantities of acid and time and temperature of oxidation will have to be determined for each specific oil.

The predetermined point to which oxidation is carried is that point at which the unstable colorforming materials previously referred to are more easily and completely removed by the subsequent action of the sulphuric acid used in treating. This point is fixed for difierent oils by preliminary oxidation and treating tests to determine the degree of dehydration and oxidation best adapted to the particular oil. By these preliminary tests a proper control of the operation of our process is obtained.

We claim as our invention:

1. The continuous method of producing light colored lubricating oils from a lubricating oil stock containing unsaturated hydrocarbons which consists of the steps of removing detectable moisture from said stock, then oxidizing the highly unsaturated hydrocarbons in the dehydrated oil stock to a predetermined point in stock to a concentrated sulphuric acid treatment,

neutralizing the acid and recovering a pale lubricating oil.

2. A process of producing light colored lubricating oils from a lubricating oil stock containing unsaturated hydrocarbons which consists of the continuous steps of removing detectable moisture from said stock, then oxidizing the highly unsaturated hydrocarbons in the dehydrated oil stock to a predetermined point in a separate zone at temperatures in excess of 200 F., and then subjecting the oil stock to a concentrated sulphuric acid treatment, neutralizing the acid and recovering a pale lubricating oil.

3. The method of producing light colored lubricating oils from lubricating oil stock containing unsaturated hydrocarbons which comprises the following steps in a single refining cycle; removing detectable moisture from said stock, oxidizing the highly unsaturated hydrocarbons in the dehydrated oil stock in a separate zone by blowing air therethrough at temperatures in excess of 200 F. and continuing the oxidation treatment to apredetermined point, then subjecting the oxidized oil to a concentrated sulphuric acid treatment with acid having a concentration of 98% and to a treatment with an alkali and recovering a pale lubricating oil and a ribbonlike sludge.

4. The method of producing light colored lubricating oils from a lubricating oil stock containing unsaturated hydrocarbons which consists in the continuous steps of removing detectable moisture irom said stock, then polymerizing substantially only the highly unsaturated hydrocarbon color-forming compounds in said dehydrated stock to form compounds more easily removable by an acid treatment, then subjecting the oil stock to a concentrated sulphuric acid treatment, neutralizing the acid and recovering a pale lubricating oil and a ribbonlike sludge.

LLOYD L. DAVIS. GRAEME ATKINSON. 

